Move to annual cropping saves tons of topsoil

August 06, 2009

CORVALLIS - There's a quiet revolution going on in the wheat fields of northeastern Oregon. Growers of dryland wheat are experimenting with planting crops every year, an approach that can save thousands of tons of topsoil.

For nearly 100 years, most growers used a summer fallow system. That is, land planted with wheat one year was plowed but left unplanted the following year to give the soil time to build up enough moisture to produce another crop.

In the early 1990s, the Columbia Basin had 625,000 acres in summer fallow a year. Annual cropping was virtually zero. Today, 16 percent of the traditional summer fallow acreage - more than 100,000 acres - is being planted every year.

"The summer fallow system is prone to erosion, which has been a chronic problem for area farmers," said Russ Karow, Oregon State University Extension agronomist. "Over the years, erosion has reduced organic matter in the soil to half its original level."

Annual cropping has become possible thanks to technological improvements such as better timing and application of fertilizer, new pesticides, and improved methods for planting crops without plowing, according to Michael Stoltz, OSU Extension regional director for 14 counties on the east side of the Cascades.

Since 1995, OSU Extension has conducted a series of demonstration projects with annual crops such as spring barley, canola, mustard and lentils. Other demonstrations involved "no-till farming," which refers to the practice of planting seeds directly in the stubble of the previous crop, eliminating the need to plow the soil.

Planting a crop every year dramatically reduces soil erosion. On high yielding wheat fields, it cuts soil erosion from 12 tons per acre under the fallow system to six tons. On lower yielding land, it reduces soil loss from five tons a year per acre to two tons.

"All of this will keep soil in the fields, decrease runoff and contribute significantly to cleaner streams, lower peak flows and healthier salmon habitat," Stoltz said.

OSU research shows winter wheat crops following alternate crops such as canola and mustard can yield about the same as winter wheat grown on fallow given normal rainfall patterns. So there may be no decrease in income with an annual crop rotation. But the annual planting system is definitely riskier than the traditional summer fallow when rainfall is below average.

"Given the success we've seen so far, the acreage planted every year is likely to expand dramatically in the next few years," Stoltz said. "We expect annual crop acreage could reach 250,000 acres - 40 percent of the traditional summer fallow acreage - by 2007, although much will depend on weather and economic conditions."

The economic payoff of annual cropping is difficult to pinpoint at this time, according to Karow. Prices farmers receive vary depending on the crop. With wheat prices down in world markets, annual crops offer growers a product other than wheat to sell in more favorable domestic and niche export markets.

Even more important, however, is the future of farming in the Columbia Basin.

"The erosion and soil deterioration associated with summer fallow practices cannot continue indefinitely. Annual cropping provides an escape from a farming system that will eventually put farmers out of business," Karow said.

Click photos to see a full-size version. Right click and save image to download.